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32 accidentally introduced to the Upper Colorado River Basin, including the Duchesne River Basin. Many of these fishes have established resident populations because of alteration of stream flows and resultant changes in physical aquatic habitats favorable to their existence. Many of these fishes; are reproducing naturally and, in some cases, out-reproducing native fishes. Presently, two-thirds of the fish species in the Colorado River system are exotic (nonnative). Nonnative fishes continue to invade endangered fish habitats through introductions, escapement, and range expansions. Some exotics are stocked in basin rivers mostly for sport fishing purposes, while other exotics are removed when encountered but still represent a major detriment to the 14 native fishes still residing in the basin. Stocking of cold water sports fishes such as trout do not appear to have a dramatic effect on native fish populations, primarily because their habitats do not overlap significantly and they are less voracious than other warm water exotics such as bass, pike, and catfish. Recovery program participants have concluded that continued stocking of trout does not represent any long-term threat to listed fishes. However, stocking of warm water fishes will be controlled and intensively monitored to ensure that physical barriers or other behavioral limitations will reduce the likelihood of interspecific competition and/or predation. On September 5, 1996, a stocking policy was completed by the three Upper Basin States and the Fish and Wildlife Service to establish procedures for stocking fish within the Upper Colorado River Basin. The Duchesne River provides a home fora number of exotic fishes, most notably smallmouth bass and channel catfish which were historically stocked in basin streams and reservoirs to accommodate recreational fishing demand (Mullan 1976). Their subsequent escapement from reservoirs, and the establishment of reproducing populations in riverine environments in the Duchesne, is still a concern today. Midview Dam and Reservoir is an off stream impoundment which contains trout, smallmouth bass, green sunfish, bluegill and carp. The reservoir is filled via direct diversion of Duchesne River flows through the Duchesne Feeder Canal. The Duchesne Feeder Canal is 15 miles long and is believed to be an impediment to nonnative fishes moving out of the reservoir, ascending the canal, and returning to the Duchesne River (Personal Communication, Mike Montoya, Ute Tribe Fish and Wildlife Dept.). Reservoir tailwaters feed into the Midview Lateral and Dry Gulch canal for irrigation purposes. Tailwaters not used for irrigation as well as irrigation return flows, however,. do return to the Duchesne River. Escapement of nonnative fishes form Midview Reservoir into the Duchesne River remains a possibility even though it may be minimal.